Strength in Numbers #200
(Read Hitting Injuries Part 1)
We need an integrated approach for preventing throwing arm injuries, but we must have the same level of scrutiny, care, and concern for the other arm. For some, that lead arm is the throwing arm, and going down with a hitting injury to the throwing arm is incredibly challenging, as athletes get back to hitting way faster than a throwing arm injury.
A lead arm injury that is a double whammy will wipe out a full season and maybe two for a two-way player or a position player who throws and hits on opposite sides.
In our courses, I communicate the importance of doing full exams at least once per month to check in on the lead arm so that deficiencies and asymmetries can be fixed. If the lead arm is your throwing arm, you can perform quick exams more often, but I still recommend checking in on the other side, as you won’t know what is lurking.
SLAP tears in baseball are a growing concern as bat speed increases and training intensifies. Ripping the labrum of the socket off the shoulder blade comes from very forceful loading on the biceps tendon that is anchored to the labrum, and the rehabilitation is complex and not linear.
In Part 2, we will explore the biomechanics involved in lead arm SLAP tears and how players can reduce injury risk through strength, balance, trunk stability, and mobility work.
The Mechanism of SLAP Tears in Hitters
There’s not much research on this—honestly, it might be one of the most understudied areas in baseball mechanics. But when you look at the follow-through, a one-handed release significantly stresses the biceps tendon.
That’s just the start. Significant differences also appear in horizontal shoulder movement, elbow flexion and extension, and how much the trunk tilts laterally during the swing.
When the lead arm is released and allowed to decelerate without assistance, shoulder force requirements spike over 100 N to keep the joint stable. If that’s your swing strategy, you better be strong… and you better respect shoulder fatigue (ref).
Our two-way pitchers already experience over-body-weight forces on the shoulder at ball release. Imagine pitching and hitting in the same game, with your throwing arm being the lead arm on the bat.
This is a slide from our Certified Pitching Biomechanist Course, where we talk about the major disparities in how the throwing arm is trained compared to what it experiences in the realities of competition. This holds true for lead arm training. An approach to raise max strength while minimizing metabolic fatigue or overly conditioning slow-twitch fibers will reduce injury risks and manage strength losses in pitching and hitting with high rates of force.
Importance of Shoulder Strength Balance
I don’t think I can stress this one enough. Research is bad on this as strength ratios considered the norm for baseball players are 66-75%, with the ER being much weaker than the IR muscles by 25% or more (ref).
One of the major factors in SLAP tear prevention is maintaining a balanced shoulder strength ratio, particularly between internal and external rotators, and between dominant and non-dominant arms.
While throwing athletes often focus on their dominant arm, position players must develop bilateral shoulder strength due to the symmetrical demands of hitting and attempt to even out the differences.
Data from an outfielder who has not had a swinging SLAP tear. What would you do in this situation to correct his imbalance?
For me, it’s identifying if the external rotators are weak, fatigable, or not recovering well, and then setting a plan to correct the imbalance by not overworking the weaker muscle group. The other thing would be managing the swing and throwing volume to ensure proper recovery and regeneration.
In this section of the Certified Pitching Biomechanist Course, we communicate the basis of fatigue-based injury mechanisms.
In pitching, we must scale workload based on changes in arm strength, and often, a coaching approach that alters the natural movement profile of the swing or an introduction of a foreign drill, such as a bottom hand drill that is unaccustomed to the athlete, could alter strength qualities.
In a two-way player who is experiencing throwing arm fatigue in both pitching and hitting, combined with introducing coaching approaches that can further challenge the recovery and regeneration of the lead arm both on the mound and at the plate, a greater extent of microtears and trauma can occur.
Distraction Force and Labral Strain
The distraction forces on the lead shoulder during the hitting motion are immense. At the high school level and beyond, angular trunk velocities can be well over 500 degrees per second, and peak lead arm speed can happen just before contact.
These rapid accelerations and decelerations place the labrum under high shear loads, especially if trunk and scapular stabilization is lacking or the ball is struck too far behind the body (ref).
There are two great references here. The image on the left indicates how the lead arm is pinched in and creates a force pushing the shoulder head toward the back on a down-and-away pitch (ref). The image on the right is from a research article I was a coauthor on that looked at the swings versus front toss and how the trunk can counter-rotate way behind for the tee and increase that horizontal abducted position of the shoulder in loading up.
Needless to say, tee placement is important early on in rehabilitation, as contact made away from the body or inconsistencies in trunk counter-rotation could heighten forces.
The swing phases studied in this research article show that the front toss swing (red line) at contact, the end of the acceleration phase, is more aligned with facing the pitcher (0 degree mark). The blue line, being the tee swing, has a much more negative move, reaching 140 degrees in counter-rotation, and at the contact point, the trunk is rotated more behind. On the front toss, shoulder forces can elevate if the ball is away and the trunk is more rotated toward the arm. On the tee, since the ball is hit more counter-rotated in loading, early extension of the lead arm to be more cross-body before the acceleration phase may drive up shoulder forces regardless of tee position.
Thoracic Spine Stability and Lead Shoulder Health
Restricted thoracic spine mobility is another overlooked contributor to SLAP injuries. When thoracic rotation is limited, the body compensates by placing more rotational demand on the shoulder, particularly the lead arm in the swing.
Inadequate rotation can prevent the hitter from creating optimal separation between the pelvis and trunk, leading to “arm-dominant” swings that increase labral stress. You want to be able to accelerate and stop the trunk at the right time.
However, if you have thoracic stiffness, I do not think a heavy, two-handed Paloff press is the way to go; instead, consider the variation below.
VIDEO – START until 1:26
This exercise from our Certified ArmCare Specialist Course is a beauty for trunk stabilization and lead arm stabilization. We package it together in this exercise so as not to stiffen the trunk too much, improve its ability to brace, and coordinate the acceleration and deceleration of the lead arm (outside arm) in the exercise. A must for two-way guys for sure.
The X-Factor
The ability to put on the brakes is very important for trunk rotational control. However, we need the elasticity and the stretch response between the hitter’s lead hip and back shoulder. If hip-shoulder separation is less than optimal, the big elastics in the body’s core region cannot stretch and recoil well. This can cause the lead arm to do too much to accelerate into ball contact.
This is a slide from our Certified Pitching Biomechanist Course. Hitting and pitching have very similar coordination patterns, and we speak about how the athlete loads and explodes from opposite hemispheres. The serape is a Mexican scarf with a criss-cross pattern, much like how our intrinsic muscles are arranged and the fascia between them.
When we have tension on the back, it stretches diagonally on the front of the body. Scapular stabilization and the ability to retract the shoulder blade will assist in peeling away the trunk from the lead hip. At weight-bearing foot plant, the closed and open chain coordination of the hip flexors, core muscles, pecs, and lats brings opposite sides of the body together contralaterally to accelerate the throwing arm or bat into contact.
Training diagonal patterns can be accomplished with many variations in lower body stance. If the opposite foot/leg is forward, that is a contralateral position. When the same side foot/leg is forward, that is an ipsilateral position.
Contralateral orientation requires pelvic stabilization to happen intrinsically. When the athlete has the ipsilateral pattern with the same leg forward as the exercising arm, the hips are blocked, and the focus is more on torso mobilization, which can increase tissue extensibility.
Heavy rotation training should be performed after throwing and hitting activities to reduce overuse and the potential of oblique strains.
Highlight Batter’s SLAP Tear Injury Prevention Strategies
To prevent SLAP tears in the lead shoulder, position players should adopt a multi-faceted approach:
- Bilateral shoulder strength development: Train with an isometric and eccentric emphasis. We call it ECON training – Eccentric after co-contraction training
- Trunk and scapular stability training: Prioritize anti-rotation and deceleration
- Thoracic spine mobility work: foam rolling, segmental mobilizations, active rotation, contralateral and ipsilateral serape-focused training
- Routine shoulder strength testing: using the ArmCare platform to track readiness
- Progressive overload in swing speed training: Start with the tee and progress with data to indicate reduced fatigue, maximum recovery, and shoulder balance
- Monitoring for signs of non-dominant arm fatigue or asymmetry: Make sure to test both arms once per month to identify any issues with the left and right arm
Final Thoughts
Final Thoughts
The lead shoulder in hitters is not passive but an active stabilizer and force absorber.
Preventing SLAP tears starts with understanding how force transmission, mobility, strength asymmetry, and sequencing contribute to labral stress.
With baseball injuries on the rise, incorporating evidence-based strength ratios, mobility assessments, and customized swing training protocols is not optional — it’s necessary.
Strength Matters Most Folks – And It’s Not Just Pitchers,
Ryan
Ryan@armcare.com
